Sabot projectile



Dec. 26, 1967 w. ENGEL SABOT PROJECTILE 2 Sheets-Sheet 1 Filed March 28,1966' w. ENGEL Dec. 26; 1967 SABOT PROJECT ILE 2 Sheets-Sheet 2 FiledMarch 28, 1966 Fig. 7 10d 17d 171d 175d 27 22d. 7/0

Fig.6

United States Patent 3,359,905 SABOT PROJECTILE Walter Engel, Zurich,Switzerland, assignor to Oerlikon- Buhrle Holding AG, Zurich,Switzerland Filed Mar. 28, 1966, Ser. No. 537,816 Claims priority,application Switzerland, Apr. 1, 1965, 4,523/ 65 9 Claims. (Cl. 102--93)ABSTRACT OF THE DISCLOSURE A discarding sabot projectile whereinprojectile member is held in a sabot under an axial prestress. Theprojectile member has a groove around the periphery thereof into whichis received a lock ring, which projects beyond the periphery of theprojectile member and is axially held within the sabot by means of anaxially adjustable member. The sabot contains a deformable supportwhich, upon firing of the projectile, is contacted by the rear surfaceof the projectile member and deformed. The deformation of the supportcauses the projectile member to rotate with the sabot, which is rotatedby the riding of the gun barrel. The resultant centrifugal force causesthe lock ring to expand radially whereby the ring releases theprojectile member from the sabot.

This invention relates to a sabot projectile adapted to be mounted on acartridge, and having a sabot member, which engages the cartridge, and aprojectile member which is supported by the sabot member. The projectilemember is held within the sabot member by locking means which is sodesigned that it can expand at right angles to the axis of theprojectile in response to selected movement thereof, whereby theprojectile member is released from the sabot member.

In a projectile of this type known in the prior art, the projectilemember is provided witha coaxial projection extending rearwardly throughthe rear end of the sabot member. However, the diameter of thisprojection is much smaller than the forward part of the projectilemember. The projectile member is disposed in the sabot member with itsannular support surfaces urging it toward the rear. That is, the endwall of the sabot acts as a first thrust face. The axial projection hasan annular groove in its periphery into which a locking element isreceived. The locking element protrudes radially beyond the peripheralsurface of the axial projection, and bears against the rear surface onthe end wall of the sabot member, thereby acting as a second thrustface, which completes the existing device for holding the projectilemember in the sabot member.

In guns with a high rate of firing, the projectile is fed axially intothe breech and is stopped suddenly in the projectile chamber from a highfeed velocity during the loading operation. As a result, the holdingunit for a projectile member of the existing type, mentioned above, isexposed to a very substantial amount of inertia when the projectilemember stops. The faces which transmit these forces to the sabot, arecomparatively small. Thus, they are often unable to withstand suchstresses and they are pressed in, or their edges are raised by materialforced out of the way, or recesses are formed in the end wall.

The intended expansion of the applicants locking element cannot occurduring introduction of his projectile into the breech and the adjacentrifling grooves of the barrel. Thus, the detachment of the projectilemember from the sabot member cannot take place under such circumstances,

The above-mentioned drawbacks in existing projectiles are particularlyserious where the projectile member is made of a material having a highspecific gravity, such as tungsten carbide or a similar material, andthe sabot, or

its thrust faces, are made of a material of low specific gravity, suchas a light alloy, both of which are basic requirements, above all else,for projectiles of this type. The

'two dangerous disadvantages are thus created. That is,

the holding unit becomes slack and the separation of the projectilemember from the sabot fails to take place.

In the know projectiles of this type, the projectile member is retainedin the sabot with a certain pretension, to improve the anchoring actionby the locking element, by means of slotted spring washers which press atwo-piece collar, which is provided with an oblique shoulder, in awedge-like manner into the groove of the extension, the groove beingequipped with a suitably designed counter shoulder. This solutionhowever suffers from the disadvantage that under the influence of theabove-mentioned substantial axial forces during loading, the obliqueshoulders slide off from each other so that the locking element, whichexpands as a result, releases the projectile member prematurely. Thus,the projectile member can move forwardly in the sabot and, under certaincircumstances, can even become separated from the sabot prior to firingso that it may become jammed in the barrel, which is dangerous.

The object of the invention is the provision of a locking mechanismwhich is capable of providing a reliable anchoring of the projectilemember in the sabot member as well as a reliable, correctly timedseparation of the two parts, but in such a manner that theabove-mentioned disadvantages are avoided.

According to the invention, this problem is primarily solved by placingthe locking unit in front of the end wall and providing at least one ofthe two thrust faces on an axially adjustable part. Also the lockingelement is gripped so that it can be released by a relative axialmovement between the projectile member and sabot during firing, afterwhich the locking element is moved out of its locking position bycentrifugal force.

The advantages of this design are as follows: arrangement of the holdingunit in front of the first thrust face and placement of the secondthrust face outside the maximum diameter of the projectile member offersthe possibility to make all the faces, which serve to support theprojectile member, much larger or at least capable of absorbing suitablecontact pressure. Moreover, the axially adjustable part allows thepretension in the holding unit, which is matched to the decelerationduring the loading operation and can be adjusted while the projectile isassembled. As a result, the locking element is completeiy prevented fromexpanding until the deformation of the first thrust face by theprojectile member creates the required axial play as a result of thefiring shock, the play allowing the locking element to expand withoutinterference as a result of centrifugal force.

Further details and suitable embodiments of the invention can be seenfrom the claims, the following description and the associated drawings,in which:

FIGURE 1 shows a central cross section of a sabot projectile embodyingthe invention;

FIGURE 2 shows an end view of the sabot projectile of similar importshall have reference to the upper and lower ends, respectively, of theprojectile and parts thereof as appearing in FIGURE 1. The terms innerand outer" andderivatives thereof shall have reference to the geometriccenter of said shell and its parts.

In FIGURE 1, the sabot projectile is comprised of the sabot member andthe projectile member 11, which are mounted upon a cartridge (notshown). The sabot 10, which is made of light alloy, for example aluminumalloy, is provided with sleeve-type extensions 102 and 103 extendingforwardly and rearwardly, respectively, away from a solid cylindricalcenter part which includes the bottom or thrust wall 101. The extensions103 fits into the open end of the cartridge or casing and remains therein a known manner until the sabot projectile is fired. The projectile 11is preferably made wholly or partially of tungsten carbide and isbasically of cylindrical shape, to which is added a point 21 extendingforwardly and a rear part 22 which is connected to a holding unit in thesabot 10. Broadly speaking, the sabot 10 is part of the projectile 11because it moves therewith when fired.

In the region of the bottom 101, the sabot 10 is encircled by the guidering 12 which is made of steel and which transmits the rotary impulsefrom the rifiing grooves in the gun barrel (not shown) to the sabot. Afurther, guide ring 13 is clamped between the flange 141 of the guidesleeve 14 and the face 104 of the extension 102 when the guide sleeve 14is threaded into the front end of the extension 102 of the sabot. Also,the periphery of the rig 13 is coaxial with the outer surface 142 of thesleeve 14. The radially inner face of sleeve 14 consists of a rear taper143 diverging toward the rear and a front taper 144 diverging toward thefront. The intersection 145 between said tapered surfaces provides theforward guide for the projectile 11 which is embraced by saidintersection.

As can be seen from FIGURE 2, the guide surface of the intersection 145is interrupted by several semicircular grooves 146 which are uniformlyspaced from each other and extend parallel with the axis of the sabot,passing through the tapered surfaces 143 and 144.

As is shown in FIGURE 1, the bottom 101 of the sabot 10 is provided witha coaxial, circular recess 105 into which is machined a further circularand coaxial recess 106 having a smaller diameter. The recess 105 isprovided for centering the rear part of the projectile 11 which has itssupport face 113 supported on an annular surface 107 around the recess105 which acts as a first thrust face.

The annular groove 111, machined into the rear part 22 of the projectile11, receives an annular locking element 15 of rectangular cross sectionand having a slot 16, the outer surface of the locking element 15 beingnumbered 151.

In addition to the guide sleeve 14, the forward extension 102 of thesabot 10 contains an axially adjustable sleeve 17, which is threadedlyreceived in said extension 102. This screwed sleeve 17 has a center bore174 (FIG- URE 3) which acts as a guide for the projectile 11. The rearend face of sleeve 17 forms a second thrust face 171. A set screw 20extends radially through the wall of the extension 102 and engages thesleeve 17 to prevent relative rotation.

Between this thrust face 171 and the rear groove wall 114, which runs atright angles to the axis of the projectile and acts as a support pointon the projectile 11, there is the above-mentioned annular lockingelement 15 which protrudes radially beyond the rear part 22 of theprojectile 11 and which is expandable under the influence of centrifugalforce. The actual rear end of the projectile 11 is also provided withfour rifling engagement faces 112 which are ground at equal angulardistances from each other and which enclose an acute angle with theprojectile axis directed toward the rear and whose intersections withthe circular support face 113 lying across the axis form chords in thissupport face 113. The four chords are located in the range of theannular first thrust face 107 of the sabot 10.

The space 18 defined between the surfaces 108 of the bottom 101, thecylindrical inner surface of the sleeve extension 172 and the secondthrust face 171 of sleeve 17, is provided for receiving the lockingelement after it has expanded.

As can be seen from FIGURE 3, the sleeve 17 is additionally providedwith two semicircular grooves 173 parallel with the axis of the sabotprojectile. These grooves 173 provide the connecting channels betweenthe annular space 19, formed between the inner wall of the extension 102of the sabot 10 and the outer face of projectile 11, and theabove-mentioned reception space 18 for the locking element 15.

The operation of the described sabot, immediately prior to firing andduring actual firing, results from its design and is as follows:

When the sabot projectile of which the sabot 10 forms the front part, issuddenly bottomed at the end of the loading operation into the sabotprojectile chamber of a gun barrel, the projectile 11, as a result ofits forward inertia causes its rear wall 114, acting as a support face,to press against the locking element 15 and which in turn pressesagainst the second thrust face 171 of sleeve 17 (FIGURE 1). However,since these support points were given a suitable pretension duringassembly by suitably dimensioned tightening of the threaded sleeve 17,and since all their faces are at right angles to the axis of impact andare sufficiently largely dimensioned, the locking element 15 alwaysremains clamped without change from assembly to the moment of firing.

However, after firing of the propellent charge, the tremendousacceleration of the sabot 10 within the gun barrel causes the rearsupport face 113 of the projectile 11 to be pressed backward against thefirst thrust face 107 with such force that the latter becomes deformedeither plastically due to upsetting or elastically due to spring action.When this happens, the projectile 11 will thus move backward relative tothe sabot 10, thereby releasing the clamping action of the lockingelement 15 against the face 171.

As a result of the upsetting action mentioned above, rifiing engagementfaces 112, which are ground on the rear part of the projectile willsimultaneously be pressed into the thrust face 107 according to onevariation of this design. They cause the projectile 11 to be positivelyengaged with the sabot 10, whereby the rifling effect upon the sabot 10is transmitted to the projectile 11, inasmuch as frictional forces aloneare not adequate to effect such transmission.

During the axial acceleration of the projectile 11 by the propellantgases, the locking element 15 is pressed against the rear groove flank114 and also made to rotate therewith, due to the resultant friction, sothat the locking element 15 will expand as a result of the centrifugalforce acting on it even before the sabot 10 leaves the gun barrel.Accordingly, the element 15 expands out of the annular groove 111 andmoves into the reception space 18 with the outer surface 151 of theelement 15 against the inner surface of the sleeve extension 172.

After the sabot 10 has left the gun barrel, the sabot 10 will undergomore severe deceleration, as a result of air resistance, than theprojectile 11, due to its annular front face. Thus, the projectile 11will move forwardly relative to the sabot 10 and will, after a shortinterval, become completely separated from the sabot.

As soon as the rear end 22 of the projectile 11 has moved out of therecess 105 in the bottom 101, air can move through the grooves 146 ofthe guide sleeve 14 into the annular space 19, and thence through thetwo groves 173 in sleeve 17 so that it can exert additional brakingaction on the bottom 101 of the base 10. The air resistance acting onthe base is thereby abruptly and very substantially increased, whichaccelerates the separation of the projectile 11 from the sabot 10.

In the following further examples, the modified components retain theirnumbering, except where their shape is changed, in which case the sufiixa is added to FIG- URE 4, and the suffix b is added to FIGURE 5, etc.Additional parts are given new numbers.

The second example shown in FIGURE 4 is distinguished from the designdescribed above (according to FIGURE 1) by the fact that a threaded part23 is screwed into the suitably matched sabot 10a from the rear endthereof. The sleeve 17 is omitted and, to make up for this, the interiorof the forward sabot extension 102a has the same shape as thatpreviously shown for sleeve 17, including a corresponding, second thrustface 171a. The bottom 101 of the sabot 10 is provided by the end wall ofthe threaded part 23 so that the latter has a cup-shaped appearance. Itis also fitted with a first thrust face 107a.

In the example shown in FIGURE 4 the operation is basically the same asthat described with reference to the first example. However, it shouldbe noted that the locking element 15 finds its second thrust face at therecessforming surface 171a of the sabot 10a. The deformation of theother thrust face 107a, however, takes place here upon the threaded part23.

The variation shown in FIGURE 5 for supporting the rear part of theprojectile 11 is formed by a special upsetting element 25 which can beplastically deformed and is inserted into a center bore 24 of bottom101b of sabot b. The upsetting element 25 is provided with an extension26 protruding beyond the bottom surface 107]; and lying opposite to thesupport face 113 of rear part 22 to act as first thrust face 26b for thesame purpose as in the preceding examples.

In the example shown in FIGURE 5 the support face 113 of rear part 22comes to rest on the surface 26b on the extension 26 of the upsettingelement 25. The cross section of the surface 26b on the upsettingelement 25 is so dimensioned that, when the propellant charge is fired,the reaction pressure of projectile 11 deforms the extension 26 untilthe support face 113 of rear part 22 finally comes to rest on the bottomsurface 107b. At that point the friction is generated which transmitsthe rotary movement from the sabot 10b to the projectile 11.

In the example shown in FIGURE 6, the sabot 100 for supporting the sameprojectile 11 has an elastically deformable first thrust face 260 whichis provided by the upper surface of a disk spring 25c which is locatedin a recess 1050 in the base bottom 1010, which is slightly deeper thanthe recess 105 (FIGURE 1). During the acceleration phase of the sabot10c the rear part 22 of the projectile 11 presses the spring 250 againstthe base bottom 101c as a result of the inertia acting on the projectile11. This causes spring 250 to undergo elastic deformation so that therear part 22 will approach the bottom surface 107c, of recess 105c,thereby releasing the clamping action upon the locking element 15.However, as soon as the acceleration of the projectile 11 diminishes,the spring force of spring 250 will overcome the inertia of theprojectile 11 so that the latter, after having been released from thelocking element 15 as a result of centrifugal force, is pressedforwardly with respect to the sabot 10c. Thus, the spring 25cconstitutes not only a means for transmitting torque from the sabot 10cto the projectile, but also a driving element which additionally helpsthe separation of the projectile 11 from the sabot 100.

FIGURE 7 shows a holding device for a projectile 11d with a modifiedrear part 22d. The forward part of projectile 11d may take exactly thesame form as described before with respect to FIGURE 1. The rear part22d is tapered rearwardly in steps to form several, successive truncatedcones while retaining an annular groove 111d which terminates at itsrear end in a support face 114d for the locking element 15d. In thisexample, the element 15d is designed in the form of a thin-walled sleevehaving lengthwise and rearwardly opening slots 27 uniformly spacedaround said sleeve. The rear part of the sleeve 15d, which contains saidslots 27, is bent inwardly to form lugs 28 substantially parallel withand near to the tapered wall 119, which is inclined relative to the axisof the shell, adjacent the wall114d.

The diameters of the support surface 113d and of the first thrust face107d are slightly smaller than in the preceding examples, as a result ofthe tapered shape of the rear part 22d. The thrust face for the lockingelement 15d is formed by an internal shoulder 171d in the threadedelement 17d, a cylindrical centering surface 172d adjoining the internalshoulder 171d and encircling the sleeve 15d. The centering surface 172dis connected to the wall surface 176d of a larger bore 18d by means of ashoulder 175d.

During assembly of the sabot 10d designed in accordance with FIGURE 7,the locking element or sleeve 15d is subjected to pressure by means ofthe threaded sleeve 17d so that it is pretensioned. The internalshoulder 171d of this sleeve 17d thus comes to rest on the cylindricalface at the front end of the locking element 15d, which makes contactwith the wall of the bore 172d. The lugs 28 of the element 15d thereforepress against the rear groove wall 114d, lying at right angles to theaxis of the sabot 10d, and thus locate the projectile 11d with itssupport face 113d on the thrust face 107d of the base bottom 101d.

As in the examples described above, the locking element 15d is releasedonly during firing when it is made to rotate. As a result of centrifugalforce created by such rotation, the lugs 28 bend outwardly around theinner edge of shoulder 175d, acting as fulcrum, as far as the wall ofbore 176d of the threaded sleeve 17d. Such bending is permitted by theacceleration of the sabot 10d which presses the projectile against thewall 107d and thereby releases the clamping pressure upon the element15d. Thus, thereafter, there is nothing to stop the projectile 11d frombecoming separated from the sabot 10d in substantially the same manneras discussed above with respect to FIGURE 1.

The five-described examples embodying the invention can be combined witheach other as far as the retaining device of the projectile isconcerned. For example, the upsetting element 25, the plate spring 250or the locking element 15d with its lugs 28 bent inward can be combinedin a sabot with a threaded part 23 inserted from the rear. Thesecombinations in turn can be extended to sabots with a threaded sleeve 17inserted from the front and a threaded element 23 inserted at the sametime from the rear. Moreover, all the methods of supporting theprojectile described above can without difliculty be applied to theprojectile 11d (according to FIG- URE 7).

In all these combinations according to FIGURES 1 and 4 to 6 the actionof the retaining device follows logically from their design.

Accordingly, although particular preferred embodiments of the inventionhave been disclosed above in detail for illustrative purposes, it willbe recognized that variations or modifications of such disclosures,which lie within the scope of the appended claims, are fullycontemplated.

The embodiments of the invention in which an excluflVe property orprivilege is claimed are defined as folows:

1. A sabot projectile adapted to be fired from the barrel of a gunhaving means for imparting rotation to said sabot projectile around alongitudinal axis parallel to its direction of movement, said sabotprojectile comprising:

a projectile body extending along the longitudinal axis and having asupporting surface on the rear end thereof and a ring groove in theperipheral surface thereof, said groove having a wall normal to saidlongitudinal axis; sabot means having a coaxial recess therein adaptedto receive said projectile body, said sabot means having means on theperiphery thereof adapted to engage said rotation imparting means, saidsabot means having front and rear opposed and longitudinally spaced stopfaces within said recess normal to said longitudinal axis, said rearstop face acting as a support for the supporting surface on saidprojectile body and adapted to be deformed by said projectile body, saidfront stop face being ring shaped and surrounding the projectile body;adjustment means for adjusting the relative axial positions of saidfront and rear stop faces; and

ringshaped safety means positioned within said ring groove and having afirst axial surface supported on said groove wall and a second axialsurface in engagement with said front stop face, the engagement forcetherebetween being controlled by said adjustment means, said safetymeans being adapted to hold said projectile body within said sabot meansuntil said sabot means attains a minimum rotational speed.

2. A sabot projectile as defined in claim 1, wherein said rear stop faceis provided on a plastic deformable portion of said sabot means, andsaid axial adjustment means prevents said safety means from moving outof engagement with said groove wall until after the deformation of saidrear stop face by said projectile body.

3. A sabot projectile as defined in claim 1, wherein said rear stop faceis provided on an elastically deformable portion of said sabot means.

4. A sabot projectile as defined in claim 2, wherein said sabot meansincludes a cylindrical housing having said recess therein, saidadjustment means including a sleeve threadedly received within therecess of said housing with said sleeve having a rear axial surfacedefining said front stop face.

5. A sabot projectile as defined in claim 2, wherein the sabot meansincludes a cylindrical housing and said adjustment means comprises ascrew member threadedly received within said housing, said screw memberhaving a front face thereon defining the rear stop face of said sabotmeans.

6. A sabot projectile as defined in claim 2, wherein said projectilebody is provided with a plurality of engagement surfaces thereonextending from said rear supporting surface, said engagement surfacesenclosing an acute angle with respect to said longitudinal axis andintersecting rear supporting surface so as to form chords there- 7. Asabot projectile as defined in claim 2, wherein said sabot means isprovided with a plastic, deformable, cylindrical projection thereonextending into said recess adjacent the rear supporting surface of saidprojectile body, the front axial face of said projection defining saidrear stop face.

8. A sabot projectile as defined in claim 3, wherein a spring plate ispositioned within the recess of said sabot means with the front surfaceof said spring plate defining said rear stop face.

9. A sabot projectile as defined in claim 6, wherein said safety meansis formed as a thin-walled sleeve having a plurality of longitudinallyextending lugs secured thereto with the rear ends of said lugs beingbent radially inwardly so as to be supported on said groove wall.

References Cited UNITED STATES PATENTS 1,209,611 12/1916 Mustin et al.10293 1,973,604 9/1934 Brandt 10292.5 2,389,846 11/ 1945 Ericson102-92.5 2,669,930 2/1954 Darby et a1. 102--93 FOREIGN PATENTS 301,2981/1920 Germany.

BENJAMIN A. BORCHELT, Primary Examiner.

W. KUJAWA, Assistant Examiner.

1. A SABOT PROJECTILE ADAPTED TO BE FIRED FROM THE BARREL OF A GUNHAVING MEANS FOR IMPARTING ROTATION TO SAID SABOT PROJECTILE AROUNG ALONGITUDINAL AXIS PARALLEL TO ITS DIRECTION OF MOVEMENT, SAID SABOTPROJECTILE COMPRISING: A PROJECTILE BODY EXTENDING ALONG THELONGITUDINAL AXIS AND HAVING A SUPPORTING SURFACE ON THE REAR ENDTHEREOF AND A RING GROOVE IN THE PERIPHERAL SURFACE THEREOF, SAID GROOVEHAVING A WALL NORMAL TO SAID LONGITUDINAL AXIS; SABOT MEANS HAVING ACOAXIAL RECESS THEREIN ADAPTED TO RECEIVE SAID PROJECTILE BODY, SAIDSABOT MEANS HAVING MEANS ON THE PERIPHERY THEREOF ADAPTED TO ENGAGE SAIDROTATION IMPARTING MEANS, SAID SABOT MEANS HAVING FRONT AND REAR OPPOSEDAND LONGITUDINALLY SPACED STOP FACES WITHIN SAID RECESS NORMAL TO SAIDLONGITUDINAL AXIS, SAID REAR STOP FACE ACTING AS A SUPPORT FOR THESUPPORTING SURFACE ON SAID PROJECTILE BODY AND ADPATED TO BE DEFORMED BYSAID PROJECTILE BODY, SAID FRONT STOP FACE BEING RING SHAPED ANDSURROUNDING THE PROJECTILE BODY; ADJUSTMENT MEANS FOR ADJUSTING THERELATIVE AXIAL POSITIONS OF SAID FRONT AND REAR STOP FACES; ANDRING-SHAPED SAFETY MEANS POSITIONED WITHIN SAID RING GROOVE AND HAVING AFIRST AXIAL SURFACE SUPPORTED ON SAID GROOVE WALL AND A SECOND AXIALSURFACE IN ENGAGEMENT WITH SAID FRONT STOP FACE, THE ENGAGEMENT FORCETHEREBETWEEN BEING CONTROLLED BY SAID ADJUSTMENT MEANS, SAID SAFETYMEANS BEING ADAPTED TO HOLD SAID PROJECTILE BODY WITHIN SAID SABOT MEANSUNTIL SAID SABOT MEANS ATTAINS A MINIMUM ROTATIONAL SPEED.